•FE analysis proved significance of soil properties and root volume in tree bending.•Asymmetrical defects significantly influence the measured inclinations/strains.•Marker tracking can evaluate ...overall tree response to loading from its deflection.•2nd derivative of the displacement reveals the effect of defects on stem deflection.
Despite continual development of the tree pulling test, there is no systematic study on the interaction of stem and root-plate stiffness in relation to tree assessment results. New methods involving numerical modelling and optical techniques provide tools for effective and deeper understanding of the interaction of stem and root-plate stiffness. Within this study, a finite element (FE) model of the tree response to static loading was developed, and the interaction between the stem and root-plate stiffness was analysed on three levels: longitudinal stem strains, root-plate inclinations and stem deflection curve. The model was validated at all three levels by comparison with experiment. Sensitivity analysis of the validated model showed a significant correlation of root-plate stiffness represented by the root volume and soil elastic modulus to the tree response. By analysing the defects in tree response, the importance of proper location for detection of strains and inclinations was demonstrated, especially regarding asymmetrical defects. A numerical estimate of the second derivative of displacement based on the Taylor approximation, was used to analyse the stem deflection curve.
A new method for investigating the detailed reaction and the energy absorption of trees during a rock impact was developed and applied to 15 subalpine Norway spruce (Picea abies L. Karst) trees. A ...wedge-shaped trolley, guided by prestressed steel wires, was mounted on a forested slope to simulate a falling rock. The trolley accelerates down the wires and hits a tree at a preselected stem height with variable energies. The tree displacements and accelerations during the impact were recorded to determine reactions and energy absorption for the stem, root-soil system, crown and the entire tree. Trees absorbed the kinetic energy of the trolley rapidly by mobilizing strain and inertia forces close to the impact location in the stem and the root-soil system. This energy was then gradually dissipated all over the tree through permanent deformations and damping. The stem assimilated more energy than the root-soil system. The tree's energy absorption capacity was limited by stem-bending stresses at impact height, by shear stresses at the stem base and by lack of resistance of the root-soil anchorage. It was positively and exponentially related to stem diameter at breast height and negatively related to impact height. The field experiment enabled a physical description of how a tree reacts to a rock impact and highlighted the most important and critical components of the tree for its energy absorption. Such descriptions should help make computer simulations of rock-forest interrelations more precise and thus improve management strategies to ensure that forests can provide protection against rockfall.
RESEARCH ON THE COMBINE HARVESTER REEL MECHANISM; III Sakai, Jun; Inoue, Eiji; Oduori, Moses Frank
JOURNAL of the JAPANESE SOCIETY of AGRICULTURAL MACHINERY,
1992/04/01, Letnik:
54, Številka:
Supplement
Journal Article
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